Bug 115216

	A simple Ada program using devel/florist to access POSIX
	process primitives encounters the error:

		px_true.adb:2:06: file "posix-implementation-ok_signals.ads" not found
		px_true.adb:2:06: "px_true (body)" depends on "posix.process_primitives (spec)"
		px_true.adb:2:06: "posix.process_primitives (spec)" depends on "posix.signals (spec)"
		px_true.adb:2:06: "posix.signals (spec)" depends on "posix.implementation.ok_signals (spec)"
		gnatmake: "px_true.adb" compilation error

	Note that posix-implementation-ok_signals.ads is internal
	to florist.

Fix: 

The problem arises because the configuration process has somehow
	become confused about the use of threads.  If, after running
	"make configure", the Makefile is altered so that the line (~26):
		SIGNALS_GENERATED =
	is changed to:
		SIGNALS_GENERATED = posix-implementation-ok_signals.ads
	the resulting system properly creates and installs the
	file posix-implementation-ok_signals.ads, but this results in
	a system with errors due to duplicate signal values.  This problem,
	in turn, seems to arise because several BSD signals are only
	defined in XSI mode or if a later version of POSIX is assumed.

	If pconfig.h is then changed to include:
		#define #define __XSI_VISIBLE   1
	near the top, the resulting system properly compiles and
	executes this program and several others with the command:
		gnatmake -I/usr/local/lib/florist -gnato px_true.adb \
		  -L/usr/local/lib -largs -lflorist && ./px_true 

	Note that there is clearly an underlying problem in the
	configuration mechanism that this workaround does not
	address.

	Also note that if the compilation is changed to include the
	"-gnato" flag, execution of the program results in the error:
		raised CONSTRAINT_ERROR : posix-signals.adb:1167 overflow check failed
	which is also some form of internal error for which I have
	not determined a workaround.
How-To-Repeat: 	Use the command:
		gnatmake -I/usr/local/lib/florist px_true.adb
	with this test program:
	------------------------- px_true.adb ------------------------
	with POSIX.Process_Primitives;
	procedure px_true is
		package PPP renames POSIX.Process_Primitives;
	begin
		PPP.Exit_Process (0);
	end px_true;
	----------------------- end px_true.adb ----------------------